1 /*- 2 * Copyright (c) 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Ronnie Kon at Mindcraft Inc., Kevin Lew and Elmer Yglesias. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#)heapsort.c 8.1 (Berkeley) 6/4/93 33 * $FreeBSD: src/lib/libc/stdlib/heapsort.c,v 1.6 2008/01/13 02:11:10 das Exp $ 34 * $DragonFly: src/lib/libc/stdlib/heapsort.c,v 1.5 2005/11/20 12:37:48 swildner Exp $ 35 */ 36 37 #include <errno.h> 38 #include <stddef.h> 39 #include <stdlib.h> 40 41 /* 42 * Swap two areas of size number of bytes. Although qsort(3) permits random 43 * blocks of memory to be sorted, sorting pointers is almost certainly the 44 * common case (and, were it not, could easily be made so). Regardless, it 45 * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer 46 * arithmetic gets lost in the time required for comparison function calls. 47 */ 48 #define SWAP(a, b, count, size, tmp) { \ 49 count = size; \ 50 do { \ 51 tmp = *a; \ 52 *a++ = *b; \ 53 *b++ = tmp; \ 54 } while (--count); \ 55 } 56 57 /* Copy one block of size size to another. */ 58 #define COPY(a, b, count, size, tmp1, tmp2) { \ 59 count = size; \ 60 tmp1 = a; \ 61 tmp2 = b; \ 62 do { \ 63 *tmp1++ = *tmp2++; \ 64 } while (--count); \ 65 } 66 67 /* 68 * Build the list into a heap, where a heap is defined such that for 69 * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N. 70 * 71 * There two cases. If j == nmemb, select largest of Ki and Kj. If 72 * j < nmemb, select largest of Ki, Kj and Kj+1. 73 */ 74 #define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \ 75 for (par_i = initval; (child_i = par_i * 2) <= nmemb; \ 76 par_i = child_i) { \ 77 child = base + child_i * size; \ 78 if (child_i < nmemb && compar(child, child + size) < 0) { \ 79 child += size; \ 80 ++child_i; \ 81 } \ 82 par = base + par_i * size; \ 83 if (compar(child, par) <= 0) \ 84 break; \ 85 SWAP(par, child, count, size, tmp); \ 86 } \ 87 } 88 89 /* 90 * Select the top of the heap and 'heapify'. Since by far the most expensive 91 * action is the call to the compar function, a considerable optimization 92 * in the average case can be achieved due to the fact that k, the displaced 93 * elememt, is ususally quite small, so it would be preferable to first 94 * heapify, always maintaining the invariant that the larger child is copied 95 * over its parent's record. 96 * 97 * Then, starting from the *bottom* of the heap, finding k's correct place, 98 * again maintianing the invariant. As a result of the invariant no element 99 * is 'lost' when k is assigned its correct place in the heap. 100 * 101 * The time savings from this optimization are on the order of 15-20% for the 102 * average case. See Knuth, Vol. 3, page 158, problem 18. 103 * 104 * XXX Don't break the #define SELECT line, below. Reiser cpp gets upset. 105 */ 106 #define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \ 107 for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \ 108 child = base + child_i * size; \ 109 if (child_i < nmemb && compar(child, child + size) < 0) { \ 110 child += size; \ 111 ++child_i; \ 112 } \ 113 par = base + par_i * size; \ 114 COPY(par, child, count, size, tmp1, tmp2); \ 115 } \ 116 for (;;) { \ 117 child_i = par_i; \ 118 par_i = child_i / 2; \ 119 child = base + child_i * size; \ 120 par = base + par_i * size; \ 121 if (child_i == 1 || compar(k, par) < 0) { \ 122 COPY(child, k, count, size, tmp1, tmp2); \ 123 break; \ 124 } \ 125 COPY(child, par, count, size, tmp1, tmp2); \ 126 } \ 127 } 128 129 /* 130 * Heapsort -- Knuth, Vol. 3, page 145. Runs in O (N lg N), both average 131 * and worst. While heapsort is faster than the worst case of quicksort, 132 * the BSD quicksort does median selection so that the chance of finding 133 * a data set that will trigger the worst case is nonexistent. Heapsort's 134 * only advantage over quicksort is that it requires little additional memory. 135 */ 136 int 137 heapsort(void *vbase, size_t nmemb, size_t size, 138 int (*compar)(const void *, const void *)) 139 { 140 size_t cnt, i, j, l; 141 char tmp, *tmp1, *tmp2; 142 char *base, *k, *p, *t; 143 144 if (nmemb <= 1) 145 return (0); 146 147 if (!size) { 148 errno = EINVAL; 149 return (-1); 150 } 151 152 if ((k = malloc(size)) == NULL) 153 return (-1); 154 155 /* 156 * Items are numbered from 1 to nmemb, so offset from size bytes 157 * below the starting address. 158 */ 159 base = (char *)vbase - size; 160 161 for (l = nmemb / 2 + 1; --l;) 162 CREATE(l, nmemb, i, j, t, p, size, cnt, tmp); 163 164 /* 165 * For each element of the heap, save the largest element into its 166 * final slot, save the displaced element (k), then recreate the 167 * heap. 168 */ 169 while (nmemb > 1) { 170 COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2); 171 COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2); 172 --nmemb; 173 SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2); 174 } 175 free(k); 176 return (0); 177 } 178